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# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this file,
# You can obtain one at
# mozilla/ --- infrastructure for SpiderMonkey's auto-loaded pretty-printers.
import re
import gdb
# Decorators for declaring pretty-printers.
# In each case, the decoratee should be a SpiderMonkey-style pretty-printer
# factory, taking both a gdb.Value instance and a TypeCache instance as
# arguments; see TypeCache, below.
def check_for_reused_pretty_printer(fn):
# Check that |fn| hasn't been registered as a pretty-printer under some
# other name already. (The 'enabled' flags used by GDB's
# 'enable/disable/info pretty-printer' commands are simply stored as
# properties of the function objects themselves, so a single function
# object can't carry the 'enabled' flags for two different printers.)
if hasattr(fn, "enabled"):
raise RuntimeError("pretty-printer function %r registered more than once" % fn)
# a dictionary mapping gdb.Type tags to pretty-printer functions.
printers_by_tag = {}
# A decorator: add the decoratee as a pretty-printer lookup function for types
# named |type_name|.
def pretty_printer(type_name):
def add(fn):
add_to_subprinter_list(fn, type_name)
printers_by_tag[type_name] = fn
return fn
return add
# a dictionary mapping gdb.Type tags to pretty-printer functions for pointers to
# that type.
ptr_printers_by_tag = {}
# A decorator: add the decoratee as a pretty-printer lookup function for
# pointers to types named |type_name|.
def ptr_pretty_printer(type_name):
def add(fn):
add_to_subprinter_list(fn, "ptr-to-" + type_name)
ptr_printers_by_tag[type_name] = fn
return fn
return add
# a dictionary mapping gdb.Type tags to pretty-printer functions for
# references to that type.
ref_printers_by_tag = {}
# A decorator: add the decoratee as a pretty-printer lookup function for
# references to instances of types named |type_name|.
def ref_pretty_printer(type_name):
def add(fn):
add_to_subprinter_list(fn, "ref-to-" + type_name)
ref_printers_by_tag[type_name] = fn
return fn
return add
# a dictionary mapping the template name portion of gdb.Type tags to
# pretty-printer functions for instantiations of that template.
template_printers_by_tag = {}
# A decorator: add the decoratee as a pretty-printer lookup function for
# instantiations of templates named |template_name|.
def template_pretty_printer(template_name):
def add(fn):
add_to_subprinter_list(fn, "instantiations-of-" + template_name)
template_printers_by_tag[template_name] = fn
return fn
return add
# A list of (REGEXP, PRINTER) pairs, such that if REGEXP (a RegexObject)
# matches the result of converting a gdb.Value's type to a string, then
# PRINTER is a pretty-printer lookup function that will probably like that
# value.
printers_by_regexp = []
# A decorator: add the decoratee as a pretty-printer factory for types
# that, when converted to a string, match |pattern|. Use |name| as the
# pretty-printer's name, when listing, enabling and disabling.
def pretty_printer_for_regexp(pattern, name):
compiled = re.compile(pattern)
def add(fn):
add_to_subprinter_list(fn, name)
printers_by_regexp.append((compiled, fn))
return fn
return add
# Forget all pretty-printer lookup functions defined in the module name
# |module_name|, if any exist. Use this at the top of each pretty-printer
# module like this:
# clear_module_printers(__name__)
def clear_module_printers(module_name):
global printers_by_tag, ptr_printers_by_tag, ref_printers_by_tag
global template_printers_by_tag, printers_by_regexp
# Remove all pretty-printers defined in the module named |module_name|
# from d.
def clear_dictionary(d):
# Walk the dictionary, building a list of keys whose entries we
# should remove. (It's not safe to delete entries from a dictionary
# while we're iterating over it.)
to_delete = []
for k, v in d.items():
if v.__module__ == module_name:
for k in to_delete:
del d[k]
# Iterate over printers_by_regexp, deleting entries from the given module.
new_list = []
for p in printers_by_regexp:
if p.__module__ == module_name:
printers_by_regexp = new_list
# Our subprinters array. The 'subprinters' attributes of all lookup
# functions returned by lookup_for_objfile point to this array instance,
# which we mutate as subprinters are added and removed.
subprinters = []
# Set up the 'name' and 'enabled' attributes on |subprinter|, and add it to our
# list of all SpiderMonkey subprinters.
def add_to_subprinter_list(subprinter, name): = name
subprinter.enabled = True
# Remove |subprinter| from our list of all SpiderMonkey subprinters.
def remove_from_subprinter_list(subprinter):
# An exception class meaning, "This objfile has no SpiderMonkey in it."
class NotSpiderMonkeyObjfileError(TypeError):
# TypeCache: a cache for frequently used information about an objfile.
# When a new SpiderMonkey objfile is loaded, we construct an instance of
# this class for it. Then, whenever we construct a pretty-printer for some
# gdb.Value, we also pass, as a second argument, the TypeCache for the
# objfile to which that value's type belongs.
# if objfile doesn't seem to have SpiderMonkey code in it, the constructor
# raises NotSpiderMonkeyObjfileError.
# Pretty-printer modules may add attributes to this to hold their own
# cached values. Such attributes should be named mod_NAME, where the module
# is named mozilla.NAME; for example, mozilla.JSString should store its
# metadata in the TypeCache's mod_JSString attribute.
class TypeCache(object):
def __init__(self, objfile):
self.objfile = objfile
# Unfortunately, the Python interface doesn't allow us to specify
# the objfile in whose scope lookups should occur. But simply
# knowing that we need to lookup the types afresh is probably
# enough.
self.void_t = gdb.lookup_type("void")
self.void_ptr_t = self.void_t.pointer()
self.uintptr_t = gdb.lookup_type("uintptr_t")
self.JSString_ptr_t = gdb.lookup_type("JSString").pointer()
self.JSSymbol_ptr_t = gdb.lookup_type("JS::Symbol").pointer()
self.JSObject_ptr_t = gdb.lookup_type("JSObject").pointer()
except gdb.error:
raise NotSpiderMonkeyObjfileError
self.mod_GCCellPtr = None
self.mod_Interpreter = None
self.mod_JSObject = None
self.mod_JSOp = None
self.mod_JSString = None
self.mod_JS_Value = None
self.mod_ExecutableAllocator = None
self.mod_IonGraph = None
# Yield a series of all the types that |t| implements, by following typedefs
# and iterating over base classes. Specifically:
# - |t| itself is the first value yielded.
# - If we yield a typedef, we later yield its definition.
# - If we yield a type with base classes, we later yield those base classes.
# - If we yield a type with some base classes that are typedefs,
# we yield all the type's base classes before following the typedefs.
# This is a hokey attempt to order the implemented types by meaningfulness when
# pretty-printed. Perhaps it is entirely misguided, and we should actually
# collect all applicable pretty-printers, and then use some ordering on the
# pretty-printers themselves.
# We may yield a type more than once (say, if it appears more than once in the
# class hierarchy).
def implemented_types(t):
# Yield all types that follow |t|.
def followers(t):
if t.code == gdb.TYPE_CODE_TYPEDEF:
for t2 in followers(
yield t2
elif is_struct_or_union(t):
base_classes = []
for f in t.fields():
if f.is_base_class:
yield f.type
for b in base_classes:
for t2 in followers(b):
yield t2
yield t
for t2 in followers(t):
yield t2
template_regexp = re.compile(r"([\w_:]+)<")
def is_struct_or_union(t):
return t.code in (gdb.TYPE_CODE_STRUCT, gdb.TYPE_CODE_UNION)
def is_struct_or_union_or_enum(t):
return t.code in (gdb.TYPE_CODE_STRUCT, gdb.TYPE_CODE_UNION, gdb.TYPE_CODE_ENUM)
# Construct and return a pretty-printer lookup function for objfile, or
# return None if the objfile doesn't contain SpiderMonkey code
# (specifically, definitions for SpiderMonkey types).
def lookup_for_objfile(objfile):
# Create a type cache for this objfile.
cache = TypeCache(objfile)
except NotSpiderMonkeyObjfileError:
if gdb.parameter("verbose"):
"objfile '%s' has no SpiderMonkey code; not registering pretty-printers\n"
% (objfile.filename,)
return None
# Return a pretty-printer for |value|, if we have one. This is the lookup
# function object we place in each gdb.Objfile's pretty-printers list, so it
# carries |name|, |enabled|, and |subprinters| attributes.
def lookup(value):
# If |table| has a pretty-printer for |tag|, apply it to |value|.
def check_table(table, tag):
if tag in table:
f = table[tag]
if f.enabled:
return f(value, cache)
return None
def check_table_by_type_name(table, t):
if t.code == gdb.TYPE_CODE_TYPEDEF:
return check_table(table, str(t))
elif is_struct_or_union_or_enum(t) and t.tag:
return check_table(table, t.tag)
return None
for t in implemented_types(value.type):
if t.code == gdb.TYPE_CODE_PTR:
for t2 in implemented_types(
p = check_table_by_type_name(ptr_printers_by_tag, t2)
if p:
return p
elif t.code == gdb.TYPE_CODE_REF:
for t2 in implemented_types(
p = check_table_by_type_name(ref_printers_by_tag, t2)
if p:
return p
p = check_table_by_type_name(printers_by_tag, t)
if p:
return p
if is_struct_or_union(t) and t.tag:
m = template_regexp.match(t.tag)
if m:
p = check_table(template_printers_by_tag,
if p:
return p
# Failing that, look for a printer in printers_by_regexp. We have
# to scan the whole list, so regexp printers should be used
# sparingly.
s = str(value.type)
for r, f in printers_by_regexp:
if f.enabled:
m = r.match(s)
if m:
p = f(value, cache)
if p:
return p
# No luck.
return None
# Give |lookup| the attributes expected of a pretty-printer with
# subprinters, for enabling and disabling. = "SpiderMonkey"
lookup.enabled = True
lookup.subprinters = subprinters
return lookup
# A base class for pretty-printers for pointer values that handles null
# pointers, by declining to construct a pretty-printer for them at all.
# Derived classes may simply assume that self.value is non-null.
# To help share code, this class can also be used with reference types.
# This class provides the following methods, which subclasses are free to
# override:
# __init__(self, value, cache): Save value and cache as properties by those names
# on the instance.
# to_string(self): format the type's name and address, as GDB would, and then
# call a 'summary' method (which the subclass must define) to produce a
# description of the referent.
# Note that pretty-printers returning a 'string' display hint must not use
# this default 'to_string' method, as GDB will take everything it returns,
# including the type name and address, as string contents.
class Pointer(object):
def __new__(cls, value, cache):
# Don't try to provide pretty-printers for NULL pointers.
if value.type.strip_typedefs().code == gdb.TYPE_CODE_PTR and value == 0:
return None
return super(Pointer, cls).__new__(cls)
def __init__(self, value, cache):
self.value = value
self.cache = cache
def to_string(self):
# See comment above.
assert not hasattr(self, "display_hint") or self.display_hint() != "string"
concrete_type = self.value.type.strip_typedefs()
if concrete_type.code == gdb.TYPE_CODE_PTR:
address = self.value.cast(self.cache.void_ptr_t)
elif concrete_type.code == gdb.TYPE_CODE_REF:
address = "@" + str(self.value.address.cast(self.cache.void_ptr_t))
assert not "mozilla.prettyprinters.Pointer applied to bad value type"
summary = self.summary()
except gdb.MemoryError as r:
summary = str(r)
v = "(%s) %s %s" % (self.value.type, address, summary)
return v
def summary(self):
raise NotImplementedError
field_enum_value = None
# Given |t|, a gdb.Type instance representing an enum type, return the
# numeric value of the enum value named |name|.
# Pre-2012-4-18 versions of GDB store the value of an enum member on the
# gdb.Field's 'bitpos' attribute; later versions store it on the 'enumval'
# attribute. This function retrieves the value from either.
def enum_value(t, name):
global field_enum_value
f = t[name]
# Monkey-patching is a-okay in polyfills! Just because.
if not field_enum_value:
if hasattr(f, "enumval"):
def field_enum_value(f):
return f.enumval
def field_enum_value(f):
return f.bitpos
return field_enum_value(f)